Max Planck derived fundamental units purely from fundamental physical constants h, c and G . Tank showed that Planck’s unit of length is a geometric-mean of two un-equal lengths; namely Compton-wavelength and Gravitational-radius of every particle; and his unit of mass is a geometric-mean of two un-equal masses, namely total mass of the universe and the smallest conceivable mass h H0 / c2 ; so the units, obtained by taking square-root of a set of fundamental physical constants, may not be truly fundamental units. Weinberg obtained a unit of mass by taking cube-root of a set of four fundamental-constants, ( h , c , G and H0 , where H0 is Hubble’s constant), so we are not sure whether the multiplication of three masses in Weinberg’s formula are of the same masses or of different ones. Therefore, here we shall derive a unit of mass without taking any square-root or cube-root. There is a strong possibility of physical existence of a particle with this mass, h H0 / c^2; and it seems that a photon decays into a lighter photon plus this new particle of mass : h H0 / c^2 .